Historically, the two-mode hybrid models have not sold well, and only yield minor improvements in overall fuel economy. In most applications, the two-mode hybrid system is rated at 20 miles per gallon in the city and 23 mpg highway.
GMI reports that it's unusual for programs like this to be shut down so close to the launch of a new vehicle – the next-generation trucks/SUVs are scheduled to debut for the 2014 model year – but that many sources within GM are not surprised about the move. These new full-size hybrids were reportedly supposed to use an updated two-mode system, featuring a smaller displacement V8 engine, upgraded battery storage (using a more modern lithium-ion pack) and revamped electric motors, according to GMI.
When contacted by Autoblog, a GM spokesperson only stated that the automaker could "not comment on future products or related technologies."